Airfoil shapes are commonly used for directional control in aircraft and marine vessels. On a marine vessel, a rudder essentially operates by deflecting water wherein the rudder moves in the direction of lower pressure as water strikes the rudder with increased force on one side and decreased force on the other side. Direction control is enhanced when a properly positioned trailing tab is employed which further reduces frictional drag thereby allowing a reduction in power necessary to move the vessel and reducing fuel consumption.
When a trailing tab is used in conjunction with marine vessel stabilizers, the efficiency of the stabilizer can also be increased. A gyroscope based stabilizer is continuously activating and positioning at least two airfoil shaped fins which project outward from the side of a vessel. In this configuration, one fin develops upward lift while the other fin develops downward lift. The combination produces a stabilizing torque which counteracts the rolling force induced by wave action.
As with any properly configured airfoil, the use of a trailing tab can further improve directional control and reduce frictional drag. The use of a trailing tab and the benefits therefrom is well known, however, the operation of the trailing tab can be improved upon by proper placement of the trailing tab driver and the elimination of complex controls.
U.S. Pat. No. 1,582,391, discloses a trailing tab for governing surfaces moving within a non-rigid medium such as water or air. The trailing tab is operated by a series of intermeshing gears to cause movement of the tab in relation to the rudder.
U.S. Pat. No. 1,661,114, discloses a device for the steering of ships by the aid of a main rudder having a trailing rudder. In the main embodiment the trailing rudder is operated by a chain or gear. In FIG. 3, a pivot point is provided by matching gear face which the service at the wheel is considerably simplified, the amount of force required in steering reduced to a fraction of that hitherto necessitated, and the steering efficiency itself essentially increased.
U.S. Pat. No. 2,813,689, discloses an articulated tab and control surface interconnected so that the articulated parts of the tab are deflected relative to each other in the same direction as they are deflected relative to the aircraft control surface which carries them.
U.S. Pat. No. 3,080,845, discloses a keel having a movable trailing tab. The keel does not rotate so the trailing tab operates as rudder.
U.S. Pat. No. 3,319,594, discloses an automatic boat steering gear which uses the reactions of the relative wind on aerodynamic surfaces exposed thereto with a trailing tab set by mechanical cable.
U.S. Pat. No. 3,678,878, discloses a self-steering arrangement for sailboats comprising a counterbalanced vane pivoted on a horizontal axis and coupled by cables to the trim tab of an auxiliary rudder.
U.S. Pat. No. 3,972,301, discloses a rudder having a trim tab. The trim tab contains a motor therein which is responsive to an electric signal such that the motor will actuate the trim tab when a signal is applied thereto such as when the ship deviates from its pre-selected course.
U.S. Pat. No. 4,024,827, discloses a vessel rudder assembly including a rudder stock bearing in the form of a cantilever beam including an internal bore through which the rudder shaft extends the rudder blade is connected to the free end of the rudder shaft, and the rudder stock bearing includes at least one rudder bearing.
U.S. Pat. No. 4,307,677, discloses a rudder having a fin which is pivotable independently thereof and with a rotor on the front edge of the rudder member and the fin between the rudder member and a guide member mounted in front of said rudder member.
U.S. Pat. No. 4,342,275, discloses a rudder assembly for marine craft wherein the main rudder carries one or more fins pivotable as well as lockable in relation to it, wherein the actuating and control devices for the fin are integrated with the rudder assembly.
U.S. Pat. No. 4,463,700, discloses a rudder for watercraft with a stabilizer articulated to the rudder blade, the stabilizer and the rudder blade being connected in articulated manner.
U.S. Pat. No. 4,510,880, discloses a ship's rudder having a flap at its trailing end, actuating apparatus for such flap comprises a sector member which is mounted on the flap at top end thereof, extending toward a rudder stock and has teeth concentric with pivot pins mounting the flap on the rudder and engaged with teeth arranged concentrically with a rudder stock on a stationary guide member surrounding the rudder stock.
U.S. Pat. No. 4,535,714, discloses an electric rudder rotor having an underwater electric motor.
U.S. Pat. No. 4,599,964, discloses a sailboat hull having a generally tapered lower hull section, whereby the lower hull section is extended rearward beneath the rudder to a point aft of the visible stern. Horizontal fins extend laterally from either side of the lower hull extension which also has a trim tab attached to its aft end.
U.S. Pat. No. 4,944,239, discloses an automatic steering control system comprising a main rudder and an active flap rudder extension on the towed vehicle controlled for independent oscillation by an active flap actuator that imparts a turning force to the flap in one direction to cause the flap and rudder to move together in an opposite direction and control means extending between the towing and a towed vehicle for automatically controlling the active flap rudder extension.
U.S. Pat. No. 5,003,904, discloses a keel assembly for a water craft having a pair of vanes spaced from and connected to the leading edge section to be disposed within a flow of water past the body. Movements of the vanes pivot the portion toward the direction of flow of the water to offset the effects of a negative pressure region occurring at the leading edge section.
U.S. Pat. No. 5,549,260, discloses a rotatable slotted cylinder, partially embedded within the contours of a tail surface, such as an aircraft tail airfoil. A longitudinal axis of the cylinder runs span wise to the airfoil at or near the three-quarter chord location. The system alters the pressures on the tail surface, thus developing lift forces necessary to counter the buffet response.
U.S. Pat. No. 6,032,602, discloses a device for guiding the flow of floating objects. The device shows a main flow body which is designed in a more flat-topped manner in the area of a leading head than in the area of a trailing end. In the flow direction, a secondary body is placed behind the trailing end, which secondary body shows a rounded cross-sectional contour. The secondary body is equipped with a flow-through recess. Furthermore, the secondary body is, regarding an axis of revolution that runs at an angle to the flow direction, guided in an adjustable manner.
U.S. Pat. No. 6,138,598, discloses a method to direct an anchored floating structure against the direction of the waves. The floating structure is provided with one or more turnable wind rudder(s) at its aft end, where said rudder(s) may be adjusted versus the direction of the wind in a manner that secures to direct the floating structure against the direction of the waves in a stable manner.
U.S. Pat. No. 6,314,900, discloses a rudder, especially for water vessels, where the main rudder blade is arranged to be in a fixedly anchored centre position with respect to the hull, and having two or more rudder flaps mounted leading and trailing on the main rudder blade and arranged to steering the vessel at high speeds, and that the main rudder blade is arranged releasable from its fixedly anchored center position, and arranged to be turnable as a whole in the usual manner, especially for steering the vessel at lower speeds.
U.S. Pat. No. 6,901,873, discloses the use of gas cavities to reduce frictional drag on underwater surfaces such as hydrofoils, struts, fins, rudders, keels, propeller blades, ship hulls, underwater bodies, and wetted surfaces in general.